This invention relates to plant propagating containers and methods of growing plants in such containers. More particularly it relates to trays used for growing plants to a certain stage and for grading, transplanting and/or packaging such plants.
The majority of young plant trays which are currently on the market are constructed using a single piece of preformed plastic material having a plurality of individual growing compartments in columns and rows. It has been found that this type of tray presents difficulties when the grower attempts to transplant the plants. Since the transplanting process is not mechanized using that type of tray, the time consuming, inaccurate and expensive manual method is used. Furthermore, the plants are often either overwatered or underwatered and the roots often grow in an unhealthy spiral fashion. Growth is also retarded because of the lack of air movement to the root system as well as around the leafy portion of the plants. Also, roots from plants in adjacent compartments sometimes grow together, particularly when soil is spilled on top of the tray.
U.S. Pat. No. 4,453,344 (now Reissue 32,808) invented by Aart Van Wingerden represents a significant advancement over the standard one piece growing tray. Van Wingerden teaches the concept of introducing air upwardly through the tray by using elongated holes or air compartments near the growing compartments to promote growth and development of the plants. The compartments are formed by adjacent sinuous strips. Van Wingerden also teaches the concept of introducing air into the length of the growing compartment which allows for a significant increase level of root ball aeration which contributes to beneficial growth and development of the plants when compared to conventional growing trays. The vertical airflow process between growing compartments and the increased root ball aeration within the growing compartments provide significant biological benefits to plant productivity including higher growth rates, more biomass, improved root morphology through air pruning of roots and the production of a more fibrous root system and the elimination of spiraled roots, increased plant hardiness through increases in lignin formation, cuticle thickness and less disease, and better performing plants after transplant. Furthermore, Van Wingerden broadly discloses the mechanization of removing the plant from the tray for transplanting.
While the Van Wingerden tray described above represents a significant advancement, the specific embodiment described therein showing sinuous strips, however, has several drawbacks. One drawback is that while the sinuous strip design permits a certain amount of mechanization in transplanting, the strips are difficult to handle and manual labor may be required, for example, in bringing the strips apart at a certain rate so as to permit the plants to drop one at a time from between the strips. Furthermore, other desirable results of mechanization such as grading and packaging are not discussed in the previous Van Wingerden patent. Furthermore, the root ball aeration as a result of the airflow between the contact point of adjacent strips could be improved. Also, soil can lodge between the contact points of adjacent strips which keeps the strips from fitting together properly.